Dendrocephalus riograndensis, Volcan, 2016

Key to the Dendrocephalus (Dendrocephalus) View in CoL species with a prominent lateral, multiramal projection, the distolateral corner bears a row of short, conical spines, and the distal margin is straight.In D. riograndensis n. sp. endopod I has the lateral projection is shaped like a long hook, the distolateral corner is produced, subquadrate, margined with long spines, the distal margin is sinuate, and the distomedial corner is triangular and acute, whereas endopod II is subquadrate and lacks setae or spines. No diagnostic characteristics were present in the female.

Six Dendrocephalus species have been previously reported from Brazil: D. brasiliensis , D. orientalis , D. goiasensis , Dendrocephalus thieryi Rabet, 2006 , D. carajaensis , and an undescribed species ( Rabet and Thiéry, 1996; Rabet, 2006; Chaves et al., 2011; Rogers et al., 2012). Our new species increases that number to seven, and is the southernmost record of the genus in Brazil. Rabet and Thiéry (1996), Rabet (2006), Chaves et al. (2011) each provided a key to the Dendrocephalus species for Brazil. Substitution couplets were provided by Rogers et al. (2012) to accommodate D. carajaensis . However, in order to facilitate identification of Dendrocephalus sensu stricto species, we present a key to all currently known species in the subgenus.

This key is based on males. This key does not include the undescribed species in Chaves et al. (2011). This key is only useful for mature males, which can be identified as being slightly larger than those females with mature eggs in the brood pouch.

1 Everted gonopods extending to abdominal segment two or three; gonopods bearing a medial subterminal tubercle and a comb plate; endopodites of first or first and second thoracopods modified, usually with cornified projection that may be spiniform or bearing one or more stout spines; temperate and tropical species ........ .................................................................................................................... Dendrocephalus View in CoL sensu stricto...................... 2

1’ Everted gonopods extending to abdominal segment three or four; gonopods with comb plate lacking; first thoracopods not modified; temperate North America .................... subgenus Dendrocephalinus Rogers, 2006

2(1) Thoracopod I with endopod subequal in length to thoracopod II endopod ................................................ 3

2’ Thoracopod I with endopod elongate, broadly ovate, two to four times longer than thoracopod II endopod ..................................................... Dendrocephalus cervicornis ( Weltner, 1890) (sensu Pereira, 1983) View in CoL [ Argentina]

3(2) Frontal appendage with branch 2A apex sharply hamulate or podiform ....................................................... 4

3’ Frontal appendage with branch 2A apex directed distally, slightly arcuate ........................................................... ........................................................................ Dendrocephalus carajaensis Rogers, Corrêa & Vieira, 2012 View in CoL [ Brazil]

4(3) Frontal appendage branch 2A sharply hamulate, apex bent 45° or greater ................................................... 5

4’ Frontal appendage branch 2A podiform ................................................................................................................... 8

5(4) Thoracopod I without a basolateral lobe or spiniform projection .................................................................. 6

5’ Thoracopod I without a basolateral lobe .................. Dendrocephalus orientalis Rabet & Thiéry, 1996 View in CoL [ Brazil]

6(5) Frontal appendage branch 2A with apex curving ............................................................................................... 7

6’ Frontal appendage branch 2A with apex bent at sharp 45° angle; thoracopod I and II endopod each with an inerm basolateral spiniform projection ....................... Dendrocephalus venezolanus Pereira, 1984 View in CoL [ Venezuela]

7(6) Frontal appendage branch 2D with all three sub-branches subequal in length; sub-branches I and II each with a proximal row of elongated spines, each four to six times longer than remaining spines ......................... ................................................................. Dendrocephalus argentinus Pereira & Belk, 1987 View in CoL [ Argentina, Paraguay]

7’ Frontal appendage branch 2D with all sub-branch II less than one third the length of sub-branch II and III; sub-branches I and II with all spines subequal in length ............................................................................................ ..................................................................... Dendrocephalus geayi Daday, 1908 View in CoL (sensu Pereira, 1983) [ Venezuela]

8(4) Thoracopod I endopod lacking a basolateral spiniform process ..................................................................... 9

8’ Thoracopod I endopod with a basolateral spiniform process ............................................................................. 10

9(8) Thoracopod I endopod similar to thoracopod II - V endopods, unmodified; frontal appendage branch 1V with anterior sub-branch distally tumid .......................................................................................................................... .................................................... Dendrocephalus brasiliensis Pesta, 1921 View in CoL (sensu Rabet & Thiérry, 1996) [ Brazil]

9’ Thoracopod I – III with endopod modified, dissimilar to thoracopod V endopod; frontal appendage branch 1V with anterior sub-branch distally tapering .............................................................................................................. .................................................................. Dendrocephalus sarmentosus Periera & Belk, 1987 View in CoL [Galapagos Islands]

10(8) Frontal appendage branch 1V with anterior sub-branch distal portion tumid ........................................ 11

10’ Frontal appendage branch 1V with anterior sub-branch distal portion tapering ......................................... 13

11(10) Thoracopod II endopod distolateral corner projecting beyond endopod distal margin ..................... 12

11’ Thoracopod II endopod distolateral corner rounded, bearing a few spines, but never projecting beyond endopod distal margin ........................................ Dendrocephalus cornutus Pereira & Belk, 1987 View in CoL [ Costa Rica]

12(11) Thoracopod I, II and III with endopod distolateral corner lobiform, projecting distolaterally well beyond the endopod distal margin; thoracopod I, II and III with endopod bearing a basolateral projection, bearing spines ........................................................................... Dendrocephalus affinis Pereira, 1984 View in CoL [ Venezuela]

12’ Thoracopod II and III only with endopod distolateral corner lobiform, projecting distolaterally beyond the endopod distal margin; thoracopod I with endopod bearing a basolateral projection bearing spines, thoracopod II with endopod bearing a basolateral spiniform inerm projection, thoracopod III endopod lacking a basolateral projection ..................................................................... Dendrocephalus thieryi Rabet, 2006 View in CoL [ Brazil]

13(10) Thoracopod I (or I through III) endopod with basolateral spiniform projection inerm ..................... 14

13’ Thoracopod I and II endopod with basolateral spiniform projection with two to four spines ......................... ............................................................................................ Dendrocephalus goiasensis Rabet & Thiéry, 1996 View in CoL [ Brazil]

14(13) Thoracopod I endopod with basolateral spiniform projection, thoracopods II and III with endopod lacking a basolateral projection ................................................................................................................................... 15

14’ Thoracopods I through III with endopod bearing a basolateral spiniform projection ...................................... .................................................. Dendrocephalus spartaenovae Margalef, 1961 View in CoL (sensu Pereira, 1983) [ Venezuela]

15(14) Frontal appendage branch 2V with apex directed distally .............................................................................. ...................................................................................... Dendrocephalus conosuris Pereira & Ruiz, 1995 View in CoL [ Argentina]

15’ Frontal appendage branch 2V with apex coiled ....................... Dendrocephalus riograndensis View in CoL n. sp. [ Brazil]